Exhaust gas combustion system

ABSTRACT

An exhaust gas combustion system advances exhaust timing by using an electric CVVT apparatus. The system may include: an air supply passage adapted to provide for passing air to be supplied to an engine; an exhaust manifold adapted to transmit exhaust gas of the engine to an exhaust passage; an air injection passage adapted to connect the air supply passage with the exhaust manifold so as to supply a part of air passing through the air supply passage to the exhaust manifold; and an air valve disposed at the air injection passage so as to selectively open or close the air injection passage. Unburned gas melded in exhaust gas may be combusted according to air supplied to the exhaust manifold.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority of Korean Patent Application Number 10-2013-0018169 filed Feb. 20, 2013, the entire contents of which application is incorporated herein for all purposes by this reference.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to an exhaust gas combustion system. More particularly, the present invention relates to an exhaust gas combustion system for an engine, using an electric continuously variable valve timing apparatus.

2. Description of Related Art

Generally, a continuously variable valve timing (CVVT) apparatus refers to an apparatus which adjusts opening and closing timing of a valve of an engine. Particularly, as the CVVT apparatus controls an intake valve in accordance with a driving condition, output of the engine and fuel efficiency may be improved, and exhaust gas may be reduced.

The opening and closing operations of exhaust and intake valves are performed by a rotation of a camshaft.

A general CVVT apparatus is a hydraulic vane type CVVT apparatus. The vane type CVVT apparatus is provided in a small space, and has a merit of being inexpensive.

However, because the vane type CVVT apparatus uses lubricant of the engine as working oil, there is a drawback in that it is difficult to expect fast and accurate response in a state in which oil pressure is low. Particularly, in a case in which engine oil pressure is not sufficient, such as in an idle state of the engine, in a high temperature state, in a start state, or the like, relative phase variation of the camshaft is difficult, and excessive leakage of exhaust gas may occur. In addition, by a shortfall of oil pressure and excessive oil viscosity at the time of cold starting, an operation of the hydraulic CVVT apparatus may be impossible. Therefore, starting is performed at a parking position fixed by a lock pin.

In a case that the hydraulic CVVT apparatus is used, opening timing of an exhaust valve being advanced may be limited. In other words, the hydraulic CVVT apparatus controls valve timing by using a method adapted to determine a maximally advanced position that enables stable idle and retard valve timing from the maximally advanced position. Therefore, the maximally advanced position is limited so as to ensure stable idle performance.

If the maximally advanced position is limited like the case that the hydraulic CVVT apparatus is used, additional devices or designs for control may be required for performing post-injection of fuel. Herein, the post-injection of fuel means a process in which fuel is secondarily injected into exhaust gas so as to completely combust unburned gas melded in the exhaust gas which is unburned in the combustion chamber.

The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention provide for an exhaust gas combustion system having advantages of advancing exhaust timing by using an electric CVVT apparatus.

Fool Various aspects of the present invention provide for an exhaust gas combustion system having further advantages of performing secondary air injection so as to completely combust unburned gas melded in exhaust gas.

An exhaust gas combustion system according to various aspects of the present invention may include: an air supply passage adapted to provide for passing air to be supplied to an engine; an exhaust manifold adapted to transmit exhaust gas of the engine to an exhaust passage; an air injection passage adapted to connect the air supply passage with the exhaust manifold so as to supply a part of air passing through the air supply passage to the exhaust manifold; and an air valve disposed at the air injection passage so as to selectively open or close the air injection passage.

Unburned gas melded in exhaust gas may be combusted according to supply of air to the exhaust manifold.

The exhaust gas combustion system may further include an electric CVVT controlling exhaust timing when exhaust gas of the engine is exhausted to the exhaust manifold.

The electric CVVT may be operated to advance the exhaust timing.

The exhaust gas combustion system may further include a supercharger supplying highly compressed air into the air supply passage.

Highly compressed air flow in the air supply passage is supplied by the supercharger such that air of the air supply passage may naturally flow into the air injection passage when the air valve is opened.

Unburned gas melded in exhaust gas to be flowing in the exhaust manifold may naturally react with oxygen of air supplied to the exhaust manifold by heat of exhaust gas, and combust.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an exemplary exhaust gas combustion system according to the present invention.

FIG. 2 is a graph showing that exhaust timing is advanced by an exemplary electric CVVT apparatus according to the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

FIG. 1 is a schematic diagram of an exhaust gas combustion system according to various embodiments of the present invention.

As shown in FIG. 1, an electric continuously variable valve timing (CVVT) apparatus 20 is applied to an exhaust gas combustion system according to various embodiments of the present invention. In addition, an exhaust gas combustion system according to various embodiments of the present invention includes an air cleaner 50, a supercharger 52, a turbocharger 70, an intercooler 42, and an air valve 60 as well as the electric CVVT apparatus 20.

The electric CVVT apparatus 20 is an apparatus which is developed to be electrically controlled in order to overcome various drawbacks of a hydraulic CVVT apparatus. Even though the electric CVVT apparatus 20 controlling exhaust timing of an engine 10 is shown in FIG. 1, the electric CVVT apparatus 20 may include another electric CVVT apparatus 20 controlling intake timing of the engine 10.

The electric CVVT apparatus 20 controlling exhaust timing is connected with a camshaft 22, and controls advance and retard by rotation of a plurality of cams 24 disposed on the camshaft 22 so as to open or close exhaust valves. The hydraulic CVVT apparatus and the electric CVVT apparatus 20 developed in order to replace the hydraulic CVVT apparatus are well-known to a person of ordinary skill in the art such that a detailed description thereof will be omitted.

The air cleaner 50 functions to remove dust from intake air inputted to the engine 10 and reduce noise caused by intake air.

The supercharger 52 is a device for increasing pressure of the intake air inputted to the engine 10. In addition, air filtered by the air cleaner 50 passes through the supercharger 52. Further, highly compressed air passing through the supercharger 52 flows into an air supply passage 54 so as to be supplied to the engine 10. Meanwhile, a part of air filtered by the air cleaner 50 selectively bypasses the supercharger 52. That is, the air cleaner 50 is directly connected with the air supply passage 54 by a bypass passage 56 not passing through the supercharger 52.

The turbocharger 70 receives air flowing into the air supply passage 54. The turbocharger 70 includes a compressor 72 and a turbine 74. The turbine 74 is connected with an exhaust manifold 30 and is rotated by flow of exhaust gas. Further, the compressor 72 compresses air received from the air supply passage 54 by torque of the turbine 74, and supplies compressed air to the engine 10.

The intercooler 42 is disposed between the compressor 72 and an intake manifold 40. That is, the intercooler 42 is disposed on an intake passage 44 transmitting air compressed by the turbocharger 70 to the engine 10 so as to cool the compressed air.

Herein, the exhaust manifold 30 is a passage to collect exhaust gas exhausted from cylinders of the engine 10 and transmit it to an exhaust passage 32. In addition, the intake manifold 40 is a passage to guide intake air to cylinders. The exhaust manifold 30 and the intake manifold 40 are well-known to a person of ordinary skill in the art. The supercharger 52 may be an electrical supercharger, and the turbocharger 70 may be a mechanical turbocharger.

Exhaust gas passing sequentially through the exhaust manifold 30, the turbine 74 of the turbocharger 70, and the exhaust passage 32 is exhausted outside of a vehicle. In addition, a first catalytic unit 80 and a second catalytic unit 82 are disposed at the exhaust passage 32. The first and second catalytic units 80 and 82 function to remove air pollution material like to nitrogen oxide melded in exhaust gas.

The air valve 60 is disposed to selectively supply air to the exhaust manifold 30. In addition, the air valve 60 is disposed at an air injection passage 62 directly connecting the air supply passage 54 and the exhaust manifold 30. Herein, the air injection passage 62 is not a passage for injecting air supplied to a combustion chamber of the engine 10, but is for directing a part of air flowing in the air supply passage 54 to the exhaust manifold 30, and the air valve 60 selectively opens and closes the air injection passage 62. Further, when the air valve 60 is opened, a high pressure is generated by the supercharger 52 such that highly compressed air passing through the air supply passage 54 is naturally flowed into the air injection passage 62. That is, secondary air injection is performed according to the operation of the air valve 60.

FIG. 2 is a graph showing that exhaust timing is advanced by an electric CVVT apparatus according to various embodiments of the present invention. In addition, a solid line and a dotted line in the left portion of FIG. 2 represent exhaust timing at which an exhaust valve is opened. Herein, the dotted line represents normal exhaust timing, and the thin solid line represents exhaust timing that is advanced by operation of the electric CVVT apparatus 20. In addition, the thick solid line in the right portion of FIG. 2 represents normal intake timing at which an intake valve is opened. Further, top dead center (TDC) and bottom dead center (BDC) of a piston are shown on a horizontal axis in FIG. 2.

As shown in FIG. 2, exhaust timing of the engine 10 is advanced according to operation of the electric CVVT apparatus 20. The exhaust process advanced by the electric CVVT apparatus 20 is more advanced as compared with the exhaust process advanced by the hydraulic CVVT apparatus in which the maximally advanced position of valve timing is limited. In other words, if valve timing is controlled by using the hydraulic CVVT apparatus such that the maximally advanced position of valve timing is limited, efficiency of secondary combustion in which unburned gas is secondarily combusted by secondary air injection may be deteriorated. In addition, control using the electric CVVT apparatus relatively advances exhaust timing as compared with control using the hydraulic CVVT apparatus.

The above-mentioned secondary air injection is technique to inject air into the exhaust manifold 30 for secondarily combusting unburned gas melded in exhaust gas in the exhaust manifold 30. Herein, the unburned gas is a mixture that is unburned in the combustion chamber.

When air is injected into the exhaust manifold 30 when the air valve 60 is opened, unburned gas reacts with oxygen of the injected air by heat energy of the exhaust gas and is naturally combusted. In addition, the natural combustion is easily performed according to the highly compressed air being injected into the exhaust manifold 30. Further, in the secondary air injection, efficiency of the secondary combustion may be improved by maximally advancing exhaust timing within a stable range.

The efficiency of the secondary combustion will hereinafter be described in detail.

Heat energy generated by combustion of a mixture is transformed to kinetic energy of a piston. At this point, if exhaust timing is advanced, an amount of heat energy to be transformed to kinetic energy is reduced. That is, the exhaust gas may have much heat energy caused by advance of the exhaust timing. Thus, exhaust gas at a high temperature has advantages that reactivity with air injected into the exhaust manifold 30 is improved and the efficiency of the secondary combust is increased.

According to various embodiments of the present invention, unburned gas melded in the exhaust gas may be completely combusted by the secondary air injection. In addition, exhaust timing may be easily advanced, and efficiency of secondary combustion of unburned gas by secondary air injection may be improved according to the electric CVVT apparatus 20 being applied for controlling valve timing. Further, a catalyst may be rapidly heated when cold starting is performed according to an improvement in efficiency of secondary combustion, and air pollution material included in exhaust gas may be minimized when the mixture is completely combusted in the exhaust manifold 30.

For convenience in explanation and accurate definition in the appended claims, the terms left and right, and etc. are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents. 

What is claimed is:
 1. An exhaust gas combustion system comprising: an air supply passage providing passing air to be supplied to an engine; an exhaust manifold transmitting exhaust gas of the engine to an exhaust passage; an air injection passage connecting the air supply passage with the exhaust manifold so as to supply a part of air passing through the air supply passage to the exhaust manifold; and an air valve disposed at the air injection passage to selectively open and close the air injection passage, wherein unburned gas melded in exhaust gas is combusted according to air supplied to the exhaust manifold.
 2. The exhaust gas combustion system of claim 1, further comprising an electric continuously variable valve timing (CVVT) apparatus controlling exhaust timing at which exhaust gas of the engine is exhausted to the exhaust manifold.
 3. The exhaust gas combustion system of claim 2, wherein the electric CVVT apparatus is operated to advance the exhaust timing.
 4. The exhaust gas combustion system of claim 1, further comprising a supercharger supplying highly compressed air into the air supply passage.
 5. The exhaust gas combustion system of claim 4, wherein highly compressed air flow in the air supply passage is supplied by the supercharger such that air of the air supply passage naturally flows into the air injection passage when the air valve is opened.
 6. The exhaust gas combustion system of claim 1, wherein unburned gas melded in exhaust gas to flow in the exhaust manifold naturally reacts with oxygen of air supplied to the exhaust manifold by heat of exhaust gas, and combusts. 